The term cross-reference (abbreviation: xref) can refer to either: * An instance within a document which refers to related information elsewhere in the same document. In both printed and online dictionaries cross-references are important because they form a network structure of relations existing between different parts of data, dictionary-internal as well as dictionary external. * In an index, a cross-reference is often denoted by See also. For example, under the term Albert Einstein in the index of a book about Nobel Laureates, there may be the cross-reference See also: Einstein, Albert. * In hypertext, cross-referencing is maintained to a document with either in-context (XRIC) or out-of-context (XROC) cross-referencing. These are similar to KWIC and KWOC. * In programming, "cross-re